Lighting device, light guide plate for lighting device, and display device including lighting device

Abstract

To provide a light guide plate that can reduce a light loss without causing any adhesive failure or contamination, and to provide a lighting device and a display device.SOLUTION: A lighting device includes: a light guide plate including an emission surface and an incident surface and provided with an irregular pattern at the incident surface, where a protrusion height is 0.01-0.4 mm; and a light-emitting device installed while being opposite to the incident surface and bonded to the irregular pattern with an adhesive agent.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] An embodiment of the present invention relates to an illumination device, a light guide plate of the illumination device, and a display device including the illumination device. [Background technology]

[0002] Liquid crystal display devices are widely used as display devices for smartphones, tablet computers, car navigation systems, etc. In general, a liquid crystal display device includes a liquid crystal display panel and an illumination device (backlight device) that is arranged on the back of the liquid crystal display panel and illuminates the liquid crystal display panel. The backlight device includes a reflective layer, a light guide plate, an optical sheet, a light source device that supplies light to be incident on the light guide plate, etc. A light source device, for example, a light emitting diode (LED), is provided facing the end face (incident surface) of the light guide plate. Usually, due to assembly errors and tolerances, a gap (air layer) is created between the placed LED and the light guide plate. Therefore, the light emitted from the LED passes through an optical path that includes the LED sealant (resin), the air layer, and the light guide plate (resin), and at this time, a large amount of light is lost due to the difference in refractive index between the air layer and the resin.

[0003] Therefore, a method has been proposed in which the air gap is filled with an optical adhesive having a refractive index equivalent to that of the resin. However, when a liquid adhesive is used in this method, the adhesive may flow out from the end face of the light guide plate, resulting in problems such as poor adhesion and contamination. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2005-78802 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the embodiments described herein is to provide a light guide plate, a lighting device, and a display device that are capable of reducing light loss without causing adhesion defects or contamination. [Means for solving the problem]

[0006] The lighting device according to the embodiment includes a light guide plate having an exit surface and an entrance surface, the entrance surface being provided with a concave-convex pattern with protrusions having a height of 0.01 to 0.4 mm, and a light emitting element disposed opposite the entrance surface and bonded to the concave-convex pattern with an adhesive. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a perspective view showing the display surface side of a liquid crystal display device according to a first embodiment. [Diagram 2] FIG. 2 is an exploded perspective view of the liquid crystal display device. [Diagram 3] FIG. 3 is an exploded perspective view of a backlight device of the liquid crystal display device. [Figure 4] 4 is a cross-sectional view of a light source side portion of the liquid crystal display device taken along line AA in FIG. [Diagram 5] FIG. 5 is a plan view showing a light source device of the backlight device. [Figure 6] FIG. 6 is a perspective view showing the light source device and a light guide plate. [Figure 7] FIG. 7 is a perspective view showing the incident surface and the concave-convex pattern of the light guide plate. [Figure 8] FIG. 8 is an enlarged perspective view of the concave-convex pattern. [Figure 9] FIG. 9 is a perspective view showing the light guide plate and an LED bonded onto the concave-convex pattern of the light guide plate. [Figure 10] FIG. 10 is an enlarged perspective view of the light guide plate and the LEDs. [Figure 11] FIG. 11 is a diagram illustrating a process of applying an adhesive to a light guide plate. [Figure 12] FIG. 12 is a schematic diagram showing the light guide plate and the LED before bonding. [Figure 13] FIG. 13 is a diagram showing a schematic diagram of a process for bonding an LED to a light guide plate. [Figure 14] FIG. 14 is a perspective view showing a concave-convex pattern of a light guide plate according to a first modified example. [Figure 15] FIG. 15 is a perspective view showing a concave-convex pattern of a light guide plate according to a second modified example. [Figure 16] FIG. 16 is a perspective view showing a concave-convex pattern of a light guide plate according to a third modified example. [Figure 17] FIG. 17 is a perspective view showing a concave-convex pattern of a light guide plate according to a fourth modified example. [Figure 18] FIG. 18 is a perspective view showing a concave-convex pattern of a light guide plate according to a fifth modified example. [Figure 19] FIG. 19 is a perspective view showing a concave-convex pattern of a light guide plate according to a sixth modified example. [Figure 20] FIG. 20 is a perspective view showing a light guide plate of a display device according to a second embodiment. [Figure 21] FIG. 21 is a perspective view showing a light guide plate and an LED of a display device according to a third embodiment. [Figure 22] FIG. 22 is a perspective view showing a light guide plate of a display device according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The disclosure is merely an example, and appropriate modifications that are within the spirit of the invention and that can be easily conceived by a person skilled in the art are naturally included in the scope of the present invention. In addition, in order to make the explanation clearer, the width, thickness, shape, etc. of each part may be shown diagrammatically compared to the actual embodiment, but these are merely examples and do not limit the interpretation of the present invention. In this specification and each figure, elements similar to those described above with respect to the previous figures may be given the same reference numerals, and detailed explanations may be omitted as appropriate.

[0009] (First embodiment) FIG. 1 is a perspective view showing the display surface side of a liquid crystal display device according to a first embodiment, and FIG. 2 is an exploded perspective view of the liquid crystal display device. The liquid crystal display device 10 can be incorporated into various electronic devices, such as smartphones, tablet terminals, mobile phones, notebook PCs, portable game consoles, electronic dictionaries, television sets, and car navigation systems.

[0010] 1 and 2, a liquid crystal display device 10 includes a display panel 12 which is an active matrix type liquid crystal display panel, a cover panel 14 which is disposed on a display surface 12a which is one surface of the display panel 12 and covers the entire display surface 12a, and a backlight device 20 which is disposed facing the rear surface which is the other surface of the display panel 12. In the figures, a first direction Y, a third direction X which is perpendicular to the first direction Y, and a second direction Z which is perpendicular to the first and third directions are defined. In this embodiment, for example, the longitudinal direction of the liquid crystal display device 10 is defined as the third direction X, the width direction is defined as the first direction Y, and the thickness direction is defined as the second direction Z.

[0011] 4 is a cross-sectional view of the light source side of the liquid crystal display device taken along line AA in FIG. 1. As shown in FIGS. 2 and 4, the display panel 12 includes a rectangular first substrate SUB1, a rectangular second substrate SUB2 disposed opposite the first substrate SUB1, and a liquid crystal layer LQ provided between the first substrate SUB1 and the second substrate SUB2. The first substrate SUB1 and the second substrate SUB2 are each formed of a transparent insulating substrate such as a glass plate or a resin plate. The peripheral portion of the second substrate SUB2 is bonded to the first substrate SUB1 by a seal material SE. A polarizing plate PL2 is attached to the surface of the second substrate SUB2 to form a display surface 12a of the display panel 12. A polarizing plate PL1 is attached to the surface of the first substrate SUB1 (the rear surface of the display panel 12).

[0012] In the display panel 12, a rectangular display area (active area) DA is provided in an area inside the sealant SE when the display surface 12a is viewed in a plan view. In this specification, a plan view refers to a state in which the display panel is viewed from the normal direction of the surface of the display panel 12. An image is displayed in the display area DA. A rectangular frame area (non-display area) ED is provided around the display area DA. The display panel 12 has a transmissive display function that selectively transmits light from the backlight device 20 to the display area DA to display an image.

[0013] In the illustrated example, a flexible printed circuit board (FPC) 22 is joined to an end portion on a short side of the first substrate SUB1 and extends outward from the display panel 12. A semiconductor element such as a driving IC chip 21 is mounted on the FPC 22 as a signal supply source that supplies signals necessary to drive the display panel 12.

[0014] 2 and 4, the cover panel 14 is made of, for example, a glass plate or an acrylic transparent resin, and has a rectangular plate shape. The cover panel 14 covers the entire display surface 12a of the display panel 12. A frame-shaped light-shielding layer RS ​​is formed on the periphery of the rear surface of the cover panel 14 (the surface on the display panel 12 side, or the surface opposite to the surface facing the viewer). The light-shielding layer RS ​​may be formed on the upper surface (display surface) of the cover panel 14. The rear surface of the cover panel 14 is attached to the polarizing plate PL2 of the display panel 12 by a light-transmitting adhesive or pressure-sensitive adhesive, for example, an adhesive sheet AD made of an optically transparent resin.

[0015] Fig. 3 is an exploded perspective view of the backlight device 20. As shown in Fig. 2, Fig. 3, and Fig. 4, the backlight device 20 constituting an illumination device includes a case (bezel) 23, a plurality of optical members arranged in the case 23, and a light source device 30 that supplies light to be incident on the optical members. The case 23 has a rectangular bottom plate 17 and a plurality of side plates erected along the side edges of the bottom plate 17. The side plates have a pair of mutually opposing long side plates 16a, 16b and a pair of mutually opposing short side plates 16c, 16d. The case 23 is integrally formed from a metal such as stainless steel (SUS). The case 23 is not limited to being made of metal, and may be molded in whole or in part from a resin such as polycarbonate.

[0016] The optical components of the backlight device 20 include a reflective sheet RE placed on a bottom plate 17 within the case 23, a light guide plate LG, and multiple sheets, for example, two sheets, a first optical sheet OS1 and a second optical sheet OS2, arranged on top of the light guide plate LG. The reflection sheet RE is formed in a rectangular shape in a plan view, and is formed to have dimensions slightly smaller than the dimensions of the bottom plate 17. The reflection sheet RE is placed on the bottom plate 17, and covers almost the entire surface of the bottom plate 17.

[0017] The light guide plate LG is a rectangular parallelepiped made of a light-transmitting resin, such as an acrylic or silicone resin. The light guide plate LG has a first main surface S1 that serves as an exit surface, a second main surface S2 on the opposite side of the first main surface S1, and a number of side surfaces. In this embodiment, one side surface on the short side of the light guide plate LG serves as an entrance surface EF. The light guide plate LG has a thickness on the other side of, for example, about 0.2 mm to 0.5 mm (200 μm to 500 μm). The light guide plate LG is disposed in the case 23 with the second main surface S2 facing the reflection sheet RE, and is placed on the reflection sheet RE. The incident surface EF of the light guide plate LG faces the short side plate (first side plate) 16d on the light source side with a gap therebetween.

[0018] According to this embodiment, the first optical sheet OS1 and the second optical sheet OS2 are, for example, a light-transmitting diffusion sheet and a prism sheet made of a synthetic resin such as polyethylene terephthalate. The optical sheets OS1 and OS2 are placed in order on the first main surface S1 of the light guide plate LG. The number of optical sheets is not limited to two, and three or more or two or less optical sheets may be used.

[0019] Next, the light source device 30 and the light guide plate LG will be described in detail. Fig. 5 is a plan view showing the end of the backlight device on the light source device side, and Fig. 6 is a perspective view showing the light source device and the light guide plate separated from each other. As shown in Figs. 5 and 6, the light source device 30 includes, for example, a long and narrow strip-shaped wiring board 32 and a plurality of light sources, for example, four light sources, mounted on the wiring board 32. A light emitting element, for example, a light emitting diode (LED) 34 is used as the light source. The wiring board 32 uses a flexible printed circuit board (FPC). The wiring board 32 has an insulating layer made of polyimide or the like, and a conductive layer, such as copper foil, formed on the insulating layer. The conductive layer is patterned to form a plurality of connection pads and a plurality of wirings. The wiring board 32 also has a connection end 36 extending from one side edge.

[0020] As shown in Fig. 6, the LED 34 has a case (package) 40 made of, for example, resin and having a substantially rectangular parallelepiped shape. The top surface of the case 40 forms a light-transmitting light-emitting surface 42, and the bottom surface opposite to the light-emitting surface 42 forms a mounting surface. A pair of connection terminals 43 (see Fig. 9) are provided on the mounting surface. Inside the case 40, an LED chip, which is a light-emitting body (light-emitting chip) (not shown), a reflector, a phosphor or encapsulating resin, bonding wires connecting the LED chip to the connection terminals, and the like are provided.

[0021] The mounting surface of the LED 34 is mounted on the wiring board 32, and the connection terminals 63 are electrically joined to connection pads of the wiring board 32. The LEDs 34 are arranged in a row on the wiring board 32 with the longitudinal direction of the case 40 aligned with the longitudinal direction (first direction Y) of the wiring board 32. The light emitting surface 42 of each LED 34 is positioned approximately parallel to the wiring board 32 and faces the incident surface EF of the light guide plate LG. 4 and 5, the wiring board 32 of the light source device 30 configured as described above is disposed opposite the short side plate 16d of the case 23 and is attached to the inner surface of the short side plate 16d, for example, with double-sided tape TP2. As a result, the wiring board 32 extends in the first direction Y and faces almost the entire incident surface EF of the light guide plate LG. Furthermore, the light emitting surface 42 of each LED 34 mounted on the wiring board 32 faces the incident surface EF of the light guide plate LG.

[0022] On the other hand, the light guide plate LG has a concave-convex pattern VP integrally formed on the incident surface EF. Fig. 7 is a perspective view showing the incident surface and the concave-convex pattern of the light guide plate, and Fig. 8 is an enlarged perspective view of the concave-convex pattern. As shown in the figure, according to this embodiment, the uneven pattern VP is formed, for example, in a sawtooth pattern. That is, the uneven pattern VP is formed by alternating a plurality of convex portions CV each having a triangular cross section with a plurality of concave portions CC each having a triangular cross section. In this embodiment, the incident surface EF of the light guide plate LG has a rectangular shape. That is, the incident surface EF has a pair of parallel long sides and a pair of parallel short sides. Hereinafter, with respect to the incident surface EF, the direction parallel to the long sides may be referred to as the longitudinal direction or first direction Y, and the direction parallel to the short sides may be referred to as the width direction, thickness direction, or second direction Z. When the incident surface EF is rectangular with a length L1 in the first direction and a width W1 in the second direction Z, each of the convex portions CV and concave portions CC extends over the entire length of the width W1 along the second direction Z. As a result, both end faces in the longitudinal direction of each of the convex portions CV are flush with the first main surface S1 and the second main surface S2 of the light guide plate LG, respectively. Note that the width W1 of the incident surface EF, i.e., the plate thickness of the light guide plate LG, is sufficiently larger than the width of the case of the LED 34.

[0023] The multiple convex portions CV and multiple concave portions CC are arranged alternately in a first direction Y (the longitudinal direction of the incident surface EF). The concave-convex pattern VP is provided over almost the entire length of the incident surface EF in the longitudinal direction Y. In this embodiment, flat regions without the concave-convex pattern are provided at both ends of the longitudinal direction of the incident surface EF, but these flat regions may be omitted. In other words, the concave-convex pattern VP may be configured to be provided to both ends of the incident surface EF in the longitudinal direction Y. 8, the protruding height h1 of each convex portion CV is formed in the range of, for example, 0.01 to 0.4 mm. In this embodiment, the multiple convex portions CV have a common protruding height h1. The pitch P1 between the convex portions CV in the longitudinal direction Y is set to, for example, 0.05 to 0.3 mm.

[0024] FIG. 9 is a perspective view showing a light guide plate and an LED bonded onto the concave-convex pattern of the light guide plate, and FIG. 10 is an enlarged perspective view showing the light guide plate and the LED. As shown in the figure, the gap (air layer) between the light emitting surface 42 of each LED 34 and the incident surface EF of the light guide plate LG is filled with adhesive Ad to fill the gap. That is, each LED 34 is adhered to the uneven pattern VP of the incident surface EF by the adhesive Ad. In one example, the adhesive Ad is made of an optically transparent resin (OCR) that has a refractive index after curing of 1.4 or more and less than the refractive index of the light guide plate LG, and a haze of 5% or less. The adhesive Ad has a viscosity in the range of 2300 to 6000 mPa s when applied.

[0025] 11, 12 and 13 are diagrams showing a schematic diagram of a process for bonding the LEDs 34 to the concave-convex pattern VP of the light guide plate LG. In bonding, first, with the incident surface EF of the light guide plate LG and the uneven pattern VP facing vertically upward, adhesive Ad is applied sequentially to predetermined positions on the uneven pattern VP using a dispenser 50, as shown in Fig. 11. Next, as shown in Fig. 12, the light source device 30 is positioned so that the light emitting surface 42 of the LED 34 faces the adhesive Ad. At this time, the light source device 30 is positioned so that a small gap is generated between the light emitting surface 42 and the adhesive Ad. In this state, the light guide plate LG and the light source device 30 are turned over approximately 180 degrees as shown in Fig. 13. Then, the adhesive Ad drips down and comes into contact with the light emitting surface 42 of the LED 34, and spreads to wet almost the entire surface of the light emitting surface 42. Thereafter, the adhesive Ad hardens, and the LED 34 is adhered onto the concave-convex pattern VP of the light guide plate LG.

[0026] In the adhesive application process and bonding process described above, the adhesive Ad applied to the concave-convex pattern VP of the light guide plate LG tends to flow out in the first direction Y and the second direction Z as shown in FIG. 10, but the presence of walls made of the convex portions CV in the first direction Y prevents the adhesive Ad from spreading widely in the first direction Y. At the same time, in the second direction Z, surface tension acts on the adhesive that tends to overflow between the concave-convex patterns VP, so the adhesive Ad is held on the concave-convex patterns VP without flowing out to the first main surface S1 and the second main surface S2. This makes it possible to ensure a sufficient application height of the adhesive Ad, improving the adhesion of the LED. At the same time, it is possible to prevent contamination caused by adhesive overflow.

[0027] 4 and 5, the light guide plate LG and the light source device 30 are arranged in the case 23 with the four LEDs 34 adhered to the concave-convex pattern VP of the incident surface EF of the light guide plate LG. The wiring board 32 of the light source device 30 faces the short side plate 16d of the case 23 and is attached to the short side plate 16d with double-sided tape TP2. As shown in FIG. 2 and FIG. 4, the backlight device 20 configured as described above is disposed facing the back surface of the display panel 12, and is attached to the first substrate SUB1 of the display panel 12 with a frame-shaped double-sided tape TP1. In this case, the double-sided tape TP1 is attached to the peripheral portion of the first substrate SUB1, i.e., the frame area ED, and its outer edge coincides with the outer edge of the first substrate SUB1. The light guide plate LG and the first and second optical sheets OS1 and OS2 are positioned parallel to the display panel 12 and face the entire surface of the display area DA. When a driving current is applied to the LEDs 34 through the wiring board 32, the LEDs 34 are turned on and emit light from the light-emitting surface 42. The light emitted from the LEDs 34 enters the light guide plate LG from the entrance surface EF of the light guide plate LG through the adhesive Ad, propagates through the light guide plate LG, or is reflected by the reflecting sheet RE, and is emitted to the display panel 12 side from the first main surface (exit surface) S1.

[0028] According to the backlight device 20 and the liquid crystal display device 10 according to the present embodiment configured as described above, the concave-convex pattern VP is provided on the incident surface EF of the light guide plate LG, and the light emitting surface 42 of the LED 34 is bonded and fixed to the concave-convex pattern VP by the adhesive applied on the concave-convex pattern VP. That is, the gap between the LED 34 and the incident surface EF of the light guide plate LG is filled with the adhesive Ad to fill the gap. Therefore, the loss of light caused by the gap can be significantly reduced. Furthermore, by providing the concave-convex pattern VP, the adhesive Ad is prevented from spreading widely around, and the LED can be bonded while maintaining a sufficient applied height of the adhesive. This improves the adhesiveness of the LED and prevents contamination due to adhesive outflow. As described above, according to the present embodiment, a light guide plate, a lighting device, and a display device capable of reducing light loss without causing adhesion failure or contamination can be obtained.

[0029] In the first embodiment, the number of LEDs 34 is not limited to four, and can be increased or decreased as necessary or according to the size of the LEDs. Also, the adhesive Ad is not limited to the above-mentioned OCR, and other optical adhesives can be appropriately selected.

[0030] Next, a backlight device and a liquid crystal display device according to modified and other embodiments will be described. In the modified and other embodiments described below, the same parts as those in the first embodiment described above are given the same reference numerals, and detailed descriptions thereof will be omitted or simplified, and the detailed description will be centered on the parts that are different from the first embodiment.

[0031] In the above-described embodiment, the concave-convex pattern of the light guide plate is not limited to a sawtooth shape, and can be modified in various ways. (First Modification) FIG. 14 is a perspective view showing a concave-convex pattern of a light guide plate according to a first modified example. As shown in the figure, according to the first modification, the light guide plate LG has a concave-convex pattern VP in which a plurality of convex portions CV, each having a semi-elliptical cross section, and a plurality of concave portions CC, each having a substantially triangular cross section, are alternately arranged. Each of the convex portions CV and concave portions CC extends across the entire width of the light guide plate LG in the second direction Z. The protruding height h1 of each of the convex portions CV is set in the range of, for example, 0.01 to 0.4 mm. The pitch P1 between the convex portions CV in the longitudinal direction Y is set to, for example, 0.05 to 0.3 mm.

[0032] (Second Modification) FIG. 15 is a perspective view showing a concave-convex pattern of a light guide plate according to a second modified example. As shown in the figure, according to the second modification, the light guide plate LG has a concave-convex pattern VP in which a plurality of convex portions CV each having a semicircular cross section and a plurality of concave portions CC each having a substantially triangular cross section are alternately arranged. Each of the convex portions CV and concave portions CC extends across the entire width of the light guide plate LG in the second direction Z. The protruding height h1 of each of the convex portions CV is set in the range of, for example, 0.01 to 0.4 mm. The pitch P1 between the convex portions CV in the longitudinal direction Y is set to, for example, 0.05 to 0.3 mm.

[0033] (Third Modification) FIG. 16 is a perspective view showing a concave-convex pattern of a light guide plate according to a first modified example. As shown in the figure, according to the third modification, the light guide plate LG has a concave-convex pattern VP in which a plurality of convex portions CV, each having a trapezoidal cross section, and a plurality of concave portions CC, each having a triangular cross section, are arranged alternately. Each of the convex portions CV and concave portions CC extends across the entire width of the light guide plate LG in the second direction Z. The protruding height h1 of each convex portion CV is formed in the range of, for example, 0.01 to 0.4 mm. The pitch P1 between the convex portions CV in the longitudinal direction Y is set to, for example, 0.05 to 0.3 mm. The width g1 of the upper base of the convex portion CV in the longitudinal direction Y is set to 1 / 5 or less of the pitch P1.

[0034] (Fourth Modification) FIG. 17 is a perspective view showing a concave-convex pattern of a light guide plate according to a fourth modified example. As shown in the figure, according to the fourth modification, the light guide plate LG has a concave-convex pattern VP in which a plurality of convex portions CV, each having a triangular cross section, and a plurality of concave portions CC, each having a trapezoidal cross section, are arranged alternately. Each of the convex portions CV and concave portions CC extends across the entire width of the light guide plate LG in the second direction Z. The protruding height h1 of each convex portion CV is formed in the range of, for example, 0.01 to 0.4 mm. The pitch P1 between the convex portions CV in the longitudinal direction Y is set to, for example, 0.05 to 0.3 mm. The width g2 of the upper base (flat portion) of the concave portion CC in the longitudinal direction Y is set to 1 / 5 or less of the pitch P1 of the convex portions CV.

[0035] (Fifth Modification) In the above-described embodiment, the extending direction of the convex portions and concave portions of the concave-convex pattern VP is not limited to the thickness direction (second direction Z) of the light guide plate LG, and can be set to any other direction. FIG. 18 is a perspective view showing a concave-convex pattern of a light guide plate according to the fifth modified example. As shown in the figure, according to the fifth modification, the concave-convex pattern VP formed on the incident surface EF of the light guide plate LG is formed, for example, in a sawtooth pattern. That is, the concave-convex pattern VP is formed by alternating a plurality of convex portions CV each having a triangular cross section with a plurality of concave portions CC each having a triangular cross section. Each of the convex portions CV and the concave portions CC extends along the longitudinal direction (first direction) Y of the light guide plate LG over almost the entire length of the incident surface EF. Moreover, the convex portions CV and the concave portions CC are alternately arranged in the width direction Z of the light guide plate LG, and are arranged over almost the entire length in the width direction. The pitch P1 of the convex portions CV in the width direction Z and the protruding height h1 of the convex portions CV are set to be the same as the pitch P1 and height h1 in the first embodiment described above.

[0036] (Sixth Modification) FIG. 19 is a perspective view showing a concave-convex pattern of a light guide plate according to a sixth modified example. As shown in the figure, according to the sixth modified example, the multiple convex portions CV and multiple concave portions CC of the concave-convex pattern VP provided on the incident surface EF of the light guide plate LG each extend in a direction inclined at an angle smaller than 90 degrees, for example, 45 degrees, with respect to the longitudinal direction Y. The multiple convex portions CV and multiple concave portions CC are provided over almost the entire length of the incident surface EF in the longitudinal direction Y and over almost the entire length in the width direction Z. The pitch P1 of the convex portions CV and the protruding height h1 of the convex portions CV are set similarly to the pitch P1 and height h1 in the first embodiment described above.

[0037] Second embodiment FIG. 20 is a perspective view showing a light guide plate of a liquid crystal display device according to the second embodiment. According to the second embodiment, in the concave-convex pattern VP of the light guide plate LG, the length W2 in the second direction Z of the convex portions CV and concave portions CC is set to be shorter than the width (plate thickness) W1 of the light guide plate LG. In one example, the length W2 is set to be 4 / 5 or more and less than 5 / 5 of the width W1, and is set to be equal to or greater than the width of the light emitting surface of the LED 34. Even when the light guide plate LG according to the second embodiment is used, the same effects as those of the first embodiment described above can be obtained.

[0038] Third embodiment 21 is a perspective view showing a light guide plate and LEDs of a liquid crystal display device according to the third embodiment. As shown in the figure, according to the third embodiment, the uneven pattern VP of the light guide plate LG is provided only in a plurality of regions to which the LEDs 34 are bonded, not on the entire incident surface EF of the light guide plate LG. That is, the uneven pattern VP of the light guide plate LG is divided into a plurality of pattern forming regions, four in this case, in the longitudinal direction Y, and a flat portion EE without a pattern is provided between each pattern forming region.

[0039] The length L2 in the first direction Y of each pattern formation region where the concave-convex pattern VP is provided is set to be longer than the length d1 in the first direction Y of the LED 34. Furthermore, in one example, each pattern formation region is formed so that the distance d2 between each end of the LED 34 in the longitudinal direction and the flat portion EE is 0.1 to 1.2 mm. The concave-convex pattern VP provided in each pattern formation region may be any of the concave-convex patterns according to the first embodiment described above or the concave-convex patterns according to Modifications 1 to 4. The LEDs 34 are adhered onto each concave-convex pattern VP with an adhesive Ad. Even when the light guide plate LG according to the third embodiment is used, the same effects as those of the first embodiment described above can be obtained.

[0040] (Fourth embodiment) FIG. 22 is a perspective view showing a light guide plate of a liquid crystal display device according to the fourth embodiment. As shown in the figure, according to the fourth embodiment, the uneven pattern VP provided on the incident surface EF of the light guide plate LG has rectangular frame-shaped convex portions CV and rectangular concave portions CC. The convex portions CV have, for example, a triangular cross-sectional shape, and their protruding height is set to be the same as the protruding height h1 of the convex portions in the first embodiment described above. The convex portions CV have a pair of long side portions extending in the longitudinal direction Y of the incident surface EF and a pair of short side portions extending in the width direction Z. Each short side portion extends over the entire length in the width direction Z, and the pair of long side portions extend along both side edges of the incident surface EF. In addition, the length L2 of each long side portion in the longitudinal direction Y is set to be longer than the length d1 (see FIG. 21) of the LED 34 to be bonded. The concave portions CC are defined inside the frame-shaped convex portions CV and have a bottom surface that is flush with the incident surface EF. When the LED 34 is bonded, the adhesive Ad is filled in the recessed portion CC, and the LED 34 is bonded to the concave-convex pattern VP and the incident surface EF of the light guide plate LG. Even when the light guide plate LG according to the fourth embodiment is used, the same effects as those of the first embodiment described above can be obtained. In the second to fourth embodiments described above, the other configurations of the liquid crystal display device and the backlight device 20 are the same as those of the liquid crystal display device and the backlight device in the first embodiment described above.

[0041] Although some embodiments and modifications of the present invention have been described, these embodiments and modifications are presented as examples and are not intended to limit the scope of the invention. The new embodiments and modifications can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. The embodiments and modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims.

[0042] All configurations that can be implemented by a person skilled in the art through appropriate design modifications based on the above-described configurations as the embodiments of the present invention are within the scope of the present invention as long as they include the gist of the present invention. For example, the shapes of the components of the liquid crystal panel and backlight device, and the case are not limited to rectangular shapes, but may be polygonal, circular, elliptical, or a combination of these shapes in a plan view. The liquid crystal display device and backlight device are not limited to flat shapes, but may be partially or entirely curved or inclined. The materials of the components are not limited to the above-described examples, and various types can be selected. Other advantageous effects brought about by the above-described embodiments that are obvious from the description in this specification or that can be appropriately thought of by a person skilled in the art are naturally understood to be brought about by the present invention. [Explanation of symbols]

[0043] 10... liquid crystal display device, 12... liquid crystal panel, 14... cover panel, 20: backlight device; 23: case; 30: light source device; 32: wiring board; 34...LED, 42...light emitting surface, LG...light guide plate, EF...incident surface, S1...output surface, VP: Convex / concave pattern, CV: Convex part, CC: Concave part, Ad: Adhesive

Claims

1. A light guide plate having an exit surface and an entry surface, wherein the entry surface is provided with an uneven pattern of protrusions with a height of 0.01 to 0.4 mm, A light-emitting element is provided facing the incident surface and bonded to the uneven pattern with an adhesive, A lighting device equipped with the following features.

2. The lighting device according to claim 1, wherein the uneven pattern includes a plurality of protrusions and a plurality of recesses each extending in a first direction, and the plurality of protrusions and a plurality of recesses are arranged alternately in a second direction intersecting the first direction.

3. The lighting device according to claim 2, wherein the arrangement pitch of the plurality of protrusions in the second direction is set to 0.05 to 0.3 mm.

4. The lighting device according to claim 1, wherein each of the aforementioned protrusions has a triangular, semi-elliptical, semi-circular, or trapezoidal cross-sectional shape.

5. The lighting device according to claim 1, wherein the light-emitting element has a light-emitting surface facing the uneven pattern, and the light-emitting surface is bonded to the uneven pattern by the adhesive.

6. The incident surface is formed in a rectangular shape having a pair of long sides and a pair of short sides. The lighting device according to claim 2, wherein the first direction is parallel to the short side, and the second direction is parallel to the long side.

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